1. Field of the Invention
This invention relates to a medical implant containing a temporary plasticizer. More particularly, this invention relates to stents containing temporary plasticizers and their methods of use.
2. Description of the State of the Art
Many medical implants undergo a great deal of strain during their manufacture and use that can result in structural failure. Structural failure can occur as a result of manipulating the implant in preparation for placing the implant in a subject and while placing the implant in a desired location in a subject. An example of such a medical implant is a stent. Stents can be used to properly hold open and, if desired, expand a passageway within a subject. Typically, a stent may be compressed, inserted into a small vessel through a catheter, and then expanded to a larger diameter in a subject.
Stent placement can serve as an important step in a variety of medical procedures such as, for example, percutaneous transluminal coronary angioplasty (PTCA)—a procedure used to treat heart disease. In PTCA, a balloon catheter is inserted through a brachial or femoral artery, positioned across a coronary artery occlusion, inflated to compress against atherosclerotic plaque to remodel the lumen of the coronary artery, deflated and withdrawn from the patient. Problems with PTCA include formation of intimal flaps or torn arterial linings, both of which can create another occlusion in the lumen of the coronary artery. Moreover, thrombosis and restenosis may occur several months after the procedure and create a need for additional angioplasty or a surgical by-pass operation. Stents are generally implanted after a PTCA to reduce occlusions, inhibit thrombosis and restenosis, and maintain patency within the lumen of the coronary artery. Examples of patents disclosing stents include U.S. Pat. Nos. 4,733,665, 4,800,882 and 4,886,062.
The manifestation of structural failure in a stent can be a formation of cracks in high-strain areas of the stent such as, for example, in the curved and intersecting regions that are extended during radial expansion of the stent from a compressed form during placement of a stent. As a result, structural failure can occur during placement of the stent in a subject and thereby affect stent performance. Accordingly, manufacturers of medical implants would benefit from new materials that can be highly strained in critical regions of the implant such as, for example, in the loop regions of a stent. These new materials can be used to form implants that can be highly strained during placement in a subject without structural failure and then become sufficiently rigid after placement such that the complications arising from structural implant failure become a thing of the past.